In many acoustic marine survey activities, it is necessary to physically inspect structures which are located beneath the surface of the sea. In the past, this work has depended primarily on placing a diver in the work location and providing life support at those ocean depths. Such operations are conditional upon weather and sea states for safe diving conditions. Examples of diver operations that use acoustic probes for acoustic surveys are illustrated by Collin's U.S. Pat. No. 4,212,258 entititled "Underwater Apparatus For Acoustically Inspecting a Submerged Object" and Nagabhusan et al.'s U.S. Pat. No. 4,832,532 entitled "Apparatus For Determining Liquid/Gas Interfaces". These teachings disclose the use of underwater ultrasonic acoustic apparatus for determining a marine structure's physical integrity and ascertaining the contents of an underwater tank structure for safe underwater work respectively.
To obviate the need for divers to perform surveys at inhospitable work sites, tethered remotely operated vehicles have become more widely used as shown by Hightower et al. in U.S. Pat. No. 4,010,619 and by Pado in U.S. Pat. No. 4,721,055. Such vehicles have incorporated power and signal means within a tether umbilical, multiplexed signal transmission means from the surface to the vehicle for command and control of the vehicle, television cameras, manipulator arms, a vehicle propulsion means, and a telemetry system to meet particular ROV system capabilities. Tools and acoustic sensors attached to ROV's is taught by "Operational Guidelines For ROVs" by the Marine Technology Society Subcommittee on ROVs, July 1, 1984, pp. 83-94.
Many underwater acoustic telemetry systems for determining the position of a submersible vehicle relative to an acoustic network, comprising multiple acoustic beacons in a long baseline configuration is well known in the art. For example, David et al.'s U.S. Pat. No. 3,864,662 entitled "Telemetry Systems Employing Active Transponders" teach of such a system that include a self calibration feature of the acoustic beacons once deployed. Another example, Spindel et al.'s U.S. Pat. No. 4,176,338 entitled "High Resolution Acoustic Navigation System" teaches of a system that use both a pulse and continuous wave acoustic beacon source, an auto-calibration feature to establish the relative coordinate beacon grid and provides high resolution positional data of the target.
For acoustic telemetry based position control of remotely operated vehicles, two approaches have been used, viz. a linear based control and a non-linear based control referred to as sliding-mode control. The linear based controller has been designed, tested and incorporated with the Towed Unmannned Submersible System (TUMS) built for the Royal Navy by Sperry Systems Management. To develop such a controller, extensive hydrodynamic analysis of the vehicle must be first performed to ascertain the vehicle's dynamic characteristics, see P. D. Rushfeldt, "Control System and Hydrodynamic Analysis For TUMS (Towed Unmanned Submersible)", Offshore Technology Conference, 14th Ann. OTC in Houston, Tex. May 3-6, 1982, pp. 595-598. The non-linear type controller in use referred to as sliding (suction) mode control is also effective for control of an underwater vehicle. This type of controller is highly adaptive to vehicle dynamic nonlinearities encountered in an underwater environment. This type of controller requires approximate hydrodynamic parameter characterization of the vehicle, see D. A. Yoerger and J. E. Slotine, "Nonlinear Trajectory Control of Autonomous Underwater Vehicles Using The Sliding Methodology", Oceans 84, Vol. 2, Conf. Wash. DC Sept. 10-12, 1984, pp. 588-593 and D. A. Yoerger and J. B. Newman, "Demonstration Of Closed-Loop Trajectory Control Of An Underwater Vehicle", Oceans 85, Vol. 2 Conf. San Diego, Calif. Nov. 12-14, 1985, pp. 1028-1033.